Re: 'git describe' is very slow on development trees with lots of commits

From: Pavel Machek <pavel@ucw.cz>
Date: Oct 31, 2012, 17:52 UTC
Message-ID: <20121031175226.GB20660@elf.ucw.cz>
In-Reply-To: <20121027133352.GB30001@gmail.com>

Hi!

Show 10 quoted lines

> (Cc:-ed the Git development list.)
> 
> * David Ahern <dsahern@gmail.com> wrote:
> 
> > PERF-VERSION-GEN and specifically the git commands are the 
> > cause of more delay than the config checks, especially when 
> > doing the build in a VM with the kernel source on an NFS 
> > mount.
> 
> Yes, I have noticed that too.

....

> The cost on this pretty fast machine is about 1 msecs per commit 
> - which adds up to about 2.5 seconds during much of the 
> development cycle.

Well... I noticed my builds when little changed are very slow... and it was due to the computation of version string. Ouch.

pavel@amd:~/mainline-altera/linux$ time git describe fixes-for-linus-506-g71ca8691 0.68user 0.22system 27.82 (0m27.820s) elapsed 3.26%CPU pavel@amd:~/mainline-altera/linux$

(Cached it is more reasonable 3 seconds, but it keeps going out of cache all the time. Uncached clean build is 3 minutes, cached is 9 seconds + time to do git describe).

Thikpad X60.

									Pavel

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